This invention relates to printed circuit board connectors having separate power or grounding contacts used for coupling printed circuit boards together.
Various concepts are known for coupling power or ground potential to a plurality of printed circuit boards in electronic equipment, in particular to wired backplanes used in computers--irrespective of the particular type of connector used on the backplane, such as for example wire-wrap connectors, metal-plate connectors, and connectors employing solder or press-in pins. Many such solutions have a common feature; one or more of the signal contacts of the printed circuit board connector are used for transfer of the power or ground potential to the individual daughterboards. It is also known to utilize a separate connection including a bus bar with an additional plug assembly for the power or ground connection.
However, on equipment as increasingly used today in computer installations, the current flowing through the power or ground contacts reaches considerable values; this is particularly true when very fast-switching semiconductor components with metal barrier layers (Schottky barrier devices) are used. Also, when connecting circuit boards together by means of connectors, it is frequently desired to ensure that the power supply or ground connection is made before the signal connections are made. This is known as a first-make-last-break feature. If the power supply is coupled through the normal signal contacts of the printed circuit board connector, several signal contacts have to be used if the current level is high, for which simultaneous and uniform connection to the several contacts has to be guaranteed. Also, since all of the signal contacts in a connector have the same length, the first-make-last-break feature for the signal contacts which are coupling the power or ground potential is difficult to achieve.
While it is known to provide a separate bus bar and plug assembly for power or ground connections, such constructions are obviously more complex and, in some cases, can lead to problems of inadequate space in the equipment.